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This Article Full Text Full Text (PDF) All Versions of this Article: 90/3/247    most recent expphysiol.2004.029637v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Guyenet, P. G. Articles by Mulkey, D. K. Search for Related Content PubMed PubMed Citation Articles by Guyenet, P. G. Articles by Mulkey, D. K. Related Collections Exchange of Views Respiratory

¹ Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA

Abstract

Central chemoreception is the mechanism by which arterial blood P_CO2 is detected by the CNS to regulate breathing. Two main theories have been proposed to account for the phenomenon. The distributed chemosensitivity theory argues that pH sensitivity is a widespread attribute of brainstem neurones and that central chemoreception results from the cumulative effects of pH on countless neurones. The specialized chemoreceptor theory envisions the existence of small and specialized populations of CNS cells (chemoreceptors) that are unique in their ability to detect very small pH fluctuations and, via specific connections, regulate a respiratory network that is itself unresponsive to pH. The recently identified CO₂-sensitive neurones of the retrotrapezoid nucleus (RTN) seem to possess most of the attributes that one would expect of such chemoreceptors. In this review we also suggest that many fewer medullary neurones are intrinsically responsive to CO₂in vivo than might have been anticipated from prior experimentation in vitro. The properties of RTN neurones provide renewed support for the specialized chemoreceptor theory of central chemoreception, proposed in the early 1960s. However, many uncertainties remain, especially as regards the molecular mechanisms of chemoreception, the type of cell that actually detects pH in vivo (neurone, glia or others) and the number and location of bona fide central chemoreceptors.

(Received 8 December 2004; accepted after revision 22 February 2005; first published online 25 February 2005)
Corresponding author P. G. Guyenet: Department of Pharmacology, University of Virginia Health System, PO Box 800735, 1300 Jefferson Park Avenue, Charlottesville, VA 22908-0735, USA. Email: pgg{at}virginia.edu